Fuel burning means for a gaseous-fluid propulsion jet



March 22, 1955 5 ALLEN 7 2,704,435

FUEL BURNING MEANS FOR A GASEOUS-FLUID PROPULSION JET Filed May 2, 1,951

l4 l6 l2 l2 l4 I6 7 2| FIGI FIGZ m/mv'roe gummy ALLEN United StatesPatent FUEL BURNING MEANS FOR A GASEOUS-FLUID PROPULSION JET SidneyAllen, Coventry, England, assignor to Armstrong Siddeley Motors Limited,Coventry, England Application May 2, 1951, Serial No. 224,098

Claims priority, application Great Britain July 17, 1950 2 Claims. (Cl.6035.6)

This invention relates to a fuel-burning means, for a gaseous-fluidpropulsion jet, of the kind having a flame stabilizing device arrangedto provide a flame such as will ensure the combustion offuelparticularly for after burning in, or re-heating, theoxygen-containing exhaust gas of a gas turbine engine for the propulsionof an aircraft, though the invention can also be applied to the burningof fuel in a ram-jet.

The importance of a flame stabilizing device, for reheat fuel, arisesfrom the fact that the exhaust gases of a gas turbine engine may have aspeed in the exhaust pipe of the order of 500 feet per second. The samedifficulty arises, in general, as regards the burning of fuel in aram-jet.

One satisfactory form of flame stabilizing device is disclosed in thespecification of co-pending patent application cl1 Io. 186,251, filedSeptember 22, 1950, now abanone The main object of the present inventionis to ensure satisfactory control of the combustion of re-heat" fuel,and, furthermore, that the high temperatures generated in the jet pipe(as a result of re-heating) will not damage the adjacent part of the jetpipe or air frame.

According to the invention, a fuel-burning means, for a gaseous-fluidpropulsion jet, includes a flame stabilizing device which is disposedrelatively to a casing, within and spaced annularly from the wall of thejet pipe, so as to be, in end elevation, within the cross-sectional areaof the casing, and means for supplying fuel to an appropriate part ofthe casing to ensure proper combustion of the fuel.

In the accompanying diagrammatic drawing:

Figure 1 is a line diagram of the tail end of the turbine of a gasturbine engine, and of the upstream end of the exhaust or jet pipethereof incorporating one form of fuel-burning means according to theinvention;

Figure 2 is a line diagram of the upstream end of a p'pe for apropulstion jet incorporating another form of fuel-burning means; and

Figure 3 is a sectional elevation of a preferred form of fuel-burningmeans in a jet pipe of a gas turbine engine, Figure 4 being a sectionalview from the right of Figure 3.

In all the figures the reference numeral 11 is applied to the flamestabilizing device, and 12 to a pipe by means of which a pilot supply offuel can be delivered thereto. It will be observed that the stabilizingdevice includes a frusto-conical casing with its smaller end upstream.

Likewise, in all the figures, the reference numeral 14 denotes thecasing which, according to the invention, is associated with the flamestabilizing device, the upstream end of the casing 14 having an annularmanifold 15 round it from which fuel is sprayed into the interior of theeasing 14, the fuel being delivered to the manifold 15 by a supply pipe16. The manifold 15 need not, of course, be exactly at the upstream endof the casing 14, and it may be disposed at any radial position in theannular space between the casing and the stabilizing device. Thereference numeral 18 is applied to the wall of the exhaust or jet pipe.

Figure 1 indicates at 20 the tail end of the turbine carrying a row ofblades 21, and abutting the tail end of the turbine is the usual innerexhaust cone 22 forming with the outer exhaust cone 23 the usual exhaustdiffuser passage leading to the upstream end of the jet pipe 18.

It will be observed that, in Figure 1, the casing 14 is disposed so asto be entirely upstream of the stabilizmg device 11. In the alternativeconstruction of Figure 2,

2,704,435 Patented Mar. 22, 1955 "ice the casing 14 is disposed so as tobe entirely downstream of the stabilizing device 11, the casing 14 beingdisposed relatively to the stabilizing device so that the flame from thelatter will enter the casing 14. In the preferred arrangement of Figures3 and 4, the casing 14 is disposed actually to encircle thestabilizing-device 11, their upstream ends being substantiallyco-planar.

The stabilizing device shown in Figures 3 and 4 has a centrally-disposedbaffle 25 at its upstream end joined to the smaller end of the casing byfixed, swirl-introducing vanes 26-as disclosed in the specificationaforesaid. The pilot supply of fuel from the pipe 12 is deliveredthrough nozzle openings 27, on opposite sides of the pipe, into andagainst the direction of the swirl of the exhaust gases in thestabilizing device. The latter is shown as being supported from thecasing 14 by angularly-spaced, streamlined struts 28, and the casing 14is shown as being supported from the jet pipe wall by means ofangularlydisposed, streamlined struts 29.

In a simple construction according to the invention, only a singlecasing 14 (and associated flame stabilizing device) would be used, thecasing 14 being cylindrical and of a size (as regards cross-sectionarea) determined by the percentage of exhaust re-heating it is desiredto obtain. That is to say, the size of the casing 14 is chosen such thatthe amount of oxygen-containing gases passing through it will besufficient to elfect complete burning of the re-heat fuel, the remainderof the exhaust gases passing externally of the casing 14. These exteriorgases will not, of course, have their temperatures raised to anydangerous extent, and, in consequence, the jet pipe is protected in theregion of the casing 14 where the reheating is being effected.

In the case which the re-heating is mainly effected in the casing 14(Figures 2 and 3, particularly), some of the re-heat fuel may bedirected onto the interior walls of the casing 14 to promote the coolingthereof, and the lower temperature of the non re-heated exhaust gasesoutside the casing will also have a cooling effect on the smg. It shouldbe understood that in those cases in which flaming gases pass from theoutlet end of the casing 14 (Figures 2 and 3), these gases will fan outand, in so doing, will mix with the exhaust gases which have passedexternally of the casing. It is desirable that a substantially uniformtemperature should be obtained across the whole area of the exhaustnozzle 30 (Figure 3) at the outlet end of the jet pipe.

In cases in which it is desired that a higher mean temperature of theexhaust gases should be obtained, use can be made of two or morecasings, as shown at 14a, 14b in Figures 3 and 4, to provide effectivecontrol of the combustion. Thus, in one alternative arrangement to thatdescribed above, a second casing 14a, of larger diameter than the first14, is arranged downstream, and preferably to overlap the outlet end, ofthe first casing 14, and is provided, preferably at its upstream end,with its own supply of re-heat fuel, by way of the manifold 15a. Ifmaximum re-heat is required (i. e., where the excess oxygen in theexhaust gases is to be used as completely as possible), it may benecessary to employ a series of such casings and fuel supplies, asindicated by the third casing 14b and manifold 15b, the upstream end ofeach preferably overlapping the downstream end of the previous one asshown. Fuel supplies for the second and third manifolds are respectivelyindicated at 16a, 16b, and supporting struts for the casings 14a, 14b,at 29a, 29b: but, as previously stated, the manifolds 15a, 15b need notbe exactly at the upstream ends of the casings 14a, 14b, or of theactual diameters of these casings.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is:

1. A fuel-burning means, for a gaseous fluid propulsion jet, including ajet pipe through which hot jet gases pass, an open-ended casing withinand spaced annularly from said jet pipe, a flame stabilizing devicedisposed relatively to said casing so as to be, in end elevation, withinthe cross-sectional area of said casing and comprising a hollow diffusermember round and through which the hot jet gases pass and within whichis to be burnt a pilot supply of fuel to produce a stable flame issuingat the downstream end, means for supplying fuel to an appropriate partof said casing to ensure proper combustion of the fuel, a second casing,of larger diameter than the first casing, within and spaced annularlyfrom said jet pipe and disposed to be mainly downstream of said firstcasing, and means for supplying fuel to an appropriate part of saidsecond casing to ensure proper combustion of this fuel.

2. A fuel-burning device for a gaseous fluid propulsion jet enginecomprising a jet pipe adapted to have oxygen bearing exhaust gases fromthe engine flow therethrough, a casing within and spaced annularly fromsaid jet pipe and disposed in the path of at least some of the exhaustgases passing through said jet pipe so that some of said gases will passthrough the easing, a flame stabilizing diffuser member of substantiallyfrusto-conical shape disposed relatively to said casing so as to be, inend elevation, within the crosssectional area of said casing anddisposed in the path of at least some of the exhaust gases passingthrough the casing so that some of said gases will pass through saiddiffuser member, said ditfuser member having its smaller end disposedupstream, pilot fuel supply means for said diffuser member near thesmaller end of the diffuser member, said pilot fuel being vaporized bysaid exhaust gases passing through said diffuser member, means forigniting said pilot supply, means for supplying fuel to an appropriatepart of said casing to ensure proper combustion of the fuel, a secondcasmg of larger diameter than the first casing disposed within andspaced annularly from said jet pipe with its major portion downstream ofsaid first casing, and means for supplying fuel to an appropriate partof said second casing to ensure proper combustion of this fuel, saidsecond casing adapted to receive re-heated exhaust gases from said firstcasing and to receive some of the exhaust gases passing through said jetpipe.

References Cited in the file of this patent UNITED STATES PATENTS2,417,445 Pinkel Mar. 18, 1947 2,517,015 Mock et al. Aug. 1, 19502,518,000 Goddard Aug. 8, 1950 2,520,388 Earl Aug. 29, 1950 2,545,495Sforzini Mar. 20, 1951 2,548,087 Williams Apr. 10, 1951 2,560,207Berggren et al. July 10, 1951 2,592,110 Berggren et al. Apr. 8, 1952

